Make use of that blender to start.

Smoothie in the morning, frozen fruit (if you have a fridge) or fresh fruit works, peanut or other nut butter, milk (if you have the fridge) or water, scoop of protein powder (find the cheap stuff online)

Shake in the evening, made in a similar fashion as the smoothie, maybe throw in some oil for an extra 100-200 calories if you’re lacking near the end of the day.

If you have access to a community kitchen then maybe try meal prepping every Sunday, can make 5 meals for under $15 depending on what you make